Golf driver having titanium alloy head and flexible shaft

ABSTRACT

A golf driver has a head which includes an alpha-beta titanium alloy body and a crown formed of a beta titanium plate which is thinner than the body and brazed to the body. The face of the club head comprises a variable-thickness beta titanium faceplate that is plasma welded to the body. Heat generated during the plasma welding causes the thin border region of the faceplate to become even more flexible to enhance the spacing action of the faceplate. Two weights are attached at the toe and heel, respectively, of the body to minimize twisting of the body during an off-center hit. Two additional weights are disposed in the sole of the body in locations causing the center of gravity to be displaced toward the heel and the back side of the club head. A graphite shaft of the driver has at least four sections of different stiffness, defining three bending points, to increase the flex action of the shaft and enable an oversized driver to return to an address position at the moment of impact.

The present application claims priority 35 U.S.C. §119 and/or §365 to U.S. Provisional Application Ser. No. 60/633,323 filed on Dec. 6, 2004.

BACKGROUND

The present invention relates to golf clubs and, in particular, to a titanium driver construction and to a shaft especially adapted for use on a titanium driver.

Titanium drivers, i.e., drivers having titanium alloy heads, have achieved popularity among golfers due to the relative light-weight properties of the metal. A light-weight head enables a golfer to increase the club head speed, which translates into increased distance. Also, a titanium head can be made larger and thus is more forgiving of off-center hits, thereby increasing directional accuracy. However, during a swing, it is more difficult to bring an oversized driver head back to the original address position at the instant of inpact, which can adversely affect the directional accuracy.

Notwithstanding the above-described advantages, there exists room for further improvement as regards driving distance and directional accuracy.

For example, it is commonly known that by lowering the location of a driver head's center of gravity, it is possible to increase the vertical height of the effective hitting area of the club face, whereby the club applies less backspin to a driven golf ball. Thus, it has been proposed to make the crown portion of a driver head in the form of a thin carbide plate which is glued to the titanium alloy body of the head. The thin carbide plate is of lighter weight (density) than the titanium alloy material which it replaces, thereby causing the head's center of gravity to be lowered, so that the height of the effective hitting area of the club face is increased. However, it has been found that the carbide crown tends to absorb and dampen the club-ball impact energy (reducing the distance of ball travel) as well as to undesirably deaden the sound of the impact.

It is also known that by increasing a horizontal distance from the driver's face to the center of gravity, i.e., increasing the “depth” of the center of gravity, a golfer is able to attain greater elevation of the driven ball, enabling the golfer to employ a club having a lower loft angle and attain greater distance.

As regards directional accuracy, it is known that optimum accuracy is attained when the ball is struck at the sweet-spot of the club face, but that an off-center hit, i.e., impact at a location offset toward the toe or heel of the club, can cause the club to twist, thereby causing the ball to hook or slide.

Furthermore, as a club head makes impact with the ball, the centrifugal force acting on the club head can cause the toe of the club head to move downwardly relative to the heel, i.e., a so-called toe-down effect, which can adversely affect the directional accuracy.

Therefore, it would be desirable to provide a titanium driver which minimizes or obviates the above-described shortcomings.

It would be further desirable to provide a titanium driver which increases the distance and directional accuracy of a struck ball.

It would also be desirable to provide a titanium driver which is more forgiving of off-center hits.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to a golf driver head comprising a body having a crown portion formed by a separate crown plate bonded at the top of the body. The body comprises an alpha-beta titanium alloy, and the crown plate comprises a beta-titanium alloy which is thinner than a surrounding portion of the body to which it is bonded.

Preferably, the crown plate is brazed to the body.

A titanium alloy faceplate is preferably bonded to a front side of the body by plasma welding along an outer periphery of the faceplate.

Another aspect of the invention relates to a golf driver head comprising a body having a crown portion formed by a separate crown plate brazed to a top portion of the body, wherein the body comprises an alpha-beta titanium alloy, and the crown plate comprises a beta-titanium alloy which is thinner than a surrounding portion of the body. A titanium alloy faceplate is bonded to a front side of the body by plasma welding along an outer periphery of the faceplate.

Yet another aspect of the invention relates to a golf driver comprising a head and a carbon shaft connected to the head. The shaft includes four sections. The first section is attached to the head. The second section is disposed adjacent to the first section. The third section is disposed adjacent to the second section. The fourth section is disposed adjacent to the third section and defines a butt end of the shaft. The first section is more flexible than the fourth section. The third section is less flexible than the fourth section and more flexible than the second section.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will become apparent from the following detailed description of a preferred embodiment thereof in connection with the accompanying drawings in which like numerals designate like elements and in which:

FIG. 1 is a front perspective view of a gold driver according to the invention.

FIG. 2 is a schematic plan view of the driver, showing the locations of four added weights.

FIG. 3 is a front perspective exploded view of the driver.

FIG. 4 is a bottom perspective view of the driver.

FIG. 5 is a schematic side view of the driver, showing the lowered center of gravity.

FIG. 6 is a schematic view of a shaft of the driver, showing the stiffness of respective sections of the shaft.

FIG. 7 is a view, similar to FIG. 6, of a prior art shaft.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A golf driver 10 depicted in FIGS. 1-4 includes a head 12 and a shaft 14. At least a major portion of the crown of the head is formed by a thin plate 16 that is attached to a body 18 of the head.

Both the body 18 and the crown 16 are formed of different respective titanium alloys. The titanium alloy of the crown 16 is stronger than the titanium alloy of the body 18, enabling the crown 16 to be considerably thinner and thus of lighter weight than would have been the case if the crown were instead formed of the same material and thickness as the body.

Preferably, the body 16 is formed of an alpha-beta titanium alloy, most preferably 6-4 ti, and the crown is preferably formed of a beta-titanium alloy, most preferably 15-3-3-3 ti. The crown thickness is can be on the order of 0.4 mm, as compared to a typical thickness of 1.0-1.5 mm for the body 18, e.g. the crown can be less than one-half the thickness of the body 18.

The crown is adhered to the body by brazing, so as to be flush with the upper surface of the body.

The use of a thin beta titanium crown that is adhered by brazing reduces the weight of the club head and thereby lowers the center of gravity. As explained earlier, and as depicted in FIG. 5, the lowering of the center of gravity CG increases the height of the effective hitting area A of the club face (such height A defined as the distance from the top of the club face to a point where the club face is intersected by a line L oriented perpendicular to the club face and passing through the center of gravity). Increasing the effective hitting area is beneficial, since a ball coming off the effective hitting area has less backspin, and an increase in distance of the drive will result. As pointed out earlier, a similar result has been attained by forming the crown of a thin carbide plate which is glued onto a titanium alloy body. The weight reduction produced by the brazed-on thin titanium crown 16 is comparable to the weight reduction attained by a prior art glued-on carbide crown. However, the carbide plate has tended to absorb and dampen the energy of the impact thereby somewhat offsetting the “longer distance” benefits that are obtained.

In contrast, by forming both the crown 16 and the body 18 of similar materials, i.e., titanium alloy, the respective densities of the two materials are relatively close (at least in comparison to the densities of carbide and titanium in the prior art driver), whereby any tendency for the crown to absorb and dampen the impact energy is minimized. For the same reason, the beta titanium crown does not appreciably deaden the sound produced upon impact, but rather produces the audible impact sound desired by players.

Mounted at the toe 20 and heel 21, respectively, of the body are weights 24 (see FIG. 2) which increase the inertia of the club at those two locations, thereby resisting a tendency for the club to twist in the event of an off-center hit, i.e., a hit which is offset toward the toe or heel. By resisting such a twisting tendency, the directional accuracy of the ball trajectory is less likely to be adversely affected by the off-center hit. Each weight 20 is preferably 2.5 gram, although other weight amounts could be used.

The weights are preferably in the form of tungsten rods, e.g., tungensten-nickel, which are welded in holes formed in the body, each hole extending parallel to a front-back centerline CL of the club head. Other materials could be used if desired. See also the inventor's concurrently filed application Ser. No. [Attorney Docket 034158-103] for a disclosure of such weights and their mounting; that concurrently filed application is incorporated by reference herein.

Attached in the sole of the club head are at least one, preferably two weights 26, 28, both located between front-to-rear centerline CL and the heel 22. Those weights serve to move the center of gravity rearwardly and away from the toe of the head. By moving the center of gravity rearwardly (deeper), a golfer is able to attain more elevation of the ball as noted earlier. By moving the center of gravity away from the toe (toward the heel), the chances for the previously described toe-down effect to occur are lessened.

The weights 26, 28 are preferably in the form of tungsten screws (e.g., tungsten-nickel) that are screwed into threaded holes of the sole. One of the weights 26, located closer to the heel, is preferably 6 grams, and the other weight 28, located closer to the back of the head, is preferably 8 grams, although other weight amounts could be used.

The front face of the head is formed by a beta titanium faceplate 30 of variable thickness that is attached to the body by plasma welding. The thickness of the faceplate is greater in the center region of the plate 30 than at an outer periphery thereof. The thick center portion is in the form of an island 32 surrounded by a thin periphery or border region 34. That variable thickness structure enables the faceplate to perform an enhanced spring action wherein the thick center region 32 of the faceplate flexes about the thin outer border region 34 of the faceplate, i.e., to perform a rebound action that produces greater driving distance.

The plasma welding is performed around the outer perimeter of the titanium alloy faceplate 30 where the faceplate meets the titanium alloy body. The intense heat of the plasma welding serves to reduce the hardness of the portion of the titanium faceplate material which is heated, e.g., the Rockwell hardness value is reduced from 36 to 28 around the thin border region 34. That enables the faceplate to flex to a greater extent about the border region, i.e., the spring action of the center thicker region 32 of the faceplate is considerably increased.

It should be noted that the use of faceplates of variable thickness has been known. It has also been known to attach a constant thickness titanium alloy faceplate to a stainless steel body by TIG (tungsten inert gas) welding. However, TIG welding does not produce enough heat to perform the above-described hardness reduction and accompanying advantages achieved by plasma welding.

The faceplate 30 is preferably formed of TVC beta titanium in the case of drivers having relatively high loft angles of 9.5°, 10.5°, and 11.5°, whereas a faceplate of 15-3 beta titanium is preferably used for drivers whose loft angle is smaller, e.g., 7.50 and 8.50. The 15-3 titanium material is stronger than the TVC material and thus produces less flexing. (Stronger golfers who can generate higher head speed, and would thus tend to employ club heads with smaller loft angles, are in less need of greater spring action.)

It is also noted that a titanium alloy faceplate attached by plasma welding weighs less than the same titanium alloy faceplace attached by TIG welding. The resulting weight reduction results in a lowered center of gravity. Alternatively, that weight savings enables weights to be added to the body in order to beneficially relocate the center of gravity (e.g., to lower the center of gravity and/or move it farther away (deeper) from the faceplate), without excessively increasing the weight of the head.

The shaft 14 preferably comprises a graphite shaft 14 of a four-section design having four flex sections 40, 42, 44, 46 defining three bending or flex points 48, 50, 52, as shown in FIG. 6, wherein the thicker left end of the shaft shown in FIG. 6 defines a butt end of the shaft. The shaft has four sections of varying hardness, wherein the degree of flexibility from most flexible to least flexible is in the order of sections 46, 40, 42, and 44, i.e., section 46 is most flexible and section 44 is least flexible.

It should be pointed out that it is known to provide a graphite shaft having three sections 60, 62, 64 with two bending points 66, 68 as shown in FIG. 7 wherein the degree of flexibility from most flexible to least flexible is in the order of sections 64, 60, 62. The stiffer sections of the prior art shaft provide control of the shaft during a swing, whereas the most flexible section 64 provides for increased head speed to improve driving distance, and to aid in bringing the head back to the original address position at the moment of impact, to improve directional accuracy. Such a prior art design has performed well, but as driver head volume has increased, the ability of the shaft to return the head to the address position has become more difficult.

However, by adding the additional section 42 between the two sections 40, 44 of the shaft, the shaft is better able to develop higher head speed at the beginning and end of the downstroke. Thus, higher-volume driver heads can be more effectively returned to the original address position at the moment of impact, resulting in better directional accuracy, as well as improved distance due to increased head speed.

Potential energy is stored in the two stiffer sections 42, 44 during a backswing, and is then released through the two more flexible sections 40, 46 during the downswing to considerably increase the swing speed through the contact zone. This makes it more likely that a heavier club head, e.g., an oversized driver, will be able to return to the address position at the moment of impact.

The second most flexible section 40 of the shaft, defining a butt end, functions primarily in a “power zone” of the backswing occurring at the top of the backswing, in order to amplify the swing arc at the end of the backswing and help increase clubhead speed at the beginning of the downstroke.

The third most flexible section 42 of the shaft functions primarily in a “power shaft zone” of the downstroke occurring just after the power zone, in order to instantly return the shaft to a straight state and make it easier to turn a large (heavy) club head.

The least flexible (most rigid) section 44 of the shaft functions primarily in “a swing plane keep zone” of the downswing following the power shift zone, in order to stabilize the swing and promote directional accuracy of the hit.

The most flexible section 46 of the shaft, i.e., the tip end, functions primarily in a “launch angle zone” of the downstroke, following the swing plane keep zone to instantly accelerate the head speed, and enable a large clubhead to return to the address position at the moment of impact, as well as to increase the launch angle.

It will be appreciated to those skilled in the art that a graphite shaft having the above-described variation in stiffness can be made by varying the thickness of the sections and/or by varying the stiffness of the graphite strands from which the shaft is formed, and/or varying the orientation of the graphite strands in a suitable manner.

The above-described invention provides a titanium driver which offers numerous advantages, including:

reduced weight due to brazing (not gluing) of the thin crown to the titanium alloy body

less damping of impact energy and impact sound, due to the use of titanium alloy (not carbide) to form the thin crown on a titanium alloy body

less tendency for the club to twist due to off-center hits by adding weight at the toe and heel

increased elevation of hits, due to movement of the center of gravity deeper

less chance for toe-down to occur by moving the center of gravity closer to the heel

increased spring action of the faceplate due to plasma welding (not TiG welding) of the faceplate to the body (also reduces head weight and lowers the center of gravity)

better control and increased speed of swing, due to the use of a graphite shaft having four sections of different hardness.

Although the present invention has been described in connection with a preferred embodiment thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims. 

1. A golf driver head comprising a body having a crown portion formed by a separate crown plate bonded at the top of the body, wherein the body comprises an alpha-beta titanium alloy, and the crown plate comprises a beta-titanium alloy which is thinner than a surrounding portion of the body to which it is bonded.
 2. The golf driver head according to claim 1, wherein the crown plate is brazed to the body.
 3. The golf driver head according to claim 1 further comprising a titanium alloy faceplate bonded to a front side of the body by plasma welding along an outer periphery of the faceplate.
 4. The golf driver head according to claim 3 wherein a center region of the faceplate is thicker than an outer periphery thereof.
 5. The golf driver head according to claim 1 further including at least one weight mounted in a sole of the body between a heel and a rear portion of the body.
 6. The golf driver head according to claim 5, further including a pair of weights mounted in a toe portion and a heel portion of the body, respectively.
 7. The golf driver head comprising a body and a titanium alloy faceplate bonded to a front side of the body by plasma welding along an outer periphery of the faceplate.
 8. A golf driver head comprising a body having a crown portion formed by a separate crown plate brazed to a top portion of the body, wherein the body comprises an alpha-beta titanium alloy, and the crown plate comprises a beta-titanium alloy which is thinner than a surrounding portion of the body, and a titanium alloy faceplate bonded to a front side of the body by plasma welding along an outer periphery of the faceplate.
 9. The golf driver head according to claim 8 wherein a center region of the faceplate is thicker than an outer periphery thereof.
 10. The golf driver head according to claim 8 further including at least one weight mounted in a sole of the body between a heel and a rear portion of the body.
 11. The golf driver head according to claim 10, further including a pair of weights mounted in a toe portion and a heel portion of the body, respectively.
 12. A golf driver comprising a head and a carbon shaft connected to the head, the shaft including four sections; a first of the sections attached to the head, a second section disposed adjacent to the first section, a third section disposed adjacent to the second section, and a fourth section disposed adjacent to the second section, and a fourth section disposed adjacent to the third section and defining a butt end of the shaft, the first section being more flexible than the fourth section; the third section being less flexible than the fourth section and more flexible than the second section. 